1. Field of the Invention
This invention relates to a process and an apparatus for joining both free ends of a rubber sheet member for use in tires to each other on a cylindrical drum.
2. Description of the Prior Art
In general, pneumatic rubber tires are a composite structure of various cords and rubber members. The rubber members include ply, breaker, belt and the like, each of which is a composite material of rubber and cords, as well as sheet-like rubber itself such as inner liner, tread ring or the like. In tire building, the rubber sheet member is usually wound on a so-called joint drum and the start- and finish-ends thereof are joined with each other to form a cylindrical shaped body irrespective of the presence of cords.
Given the recent trend for energy-saving, it is desired to automate the joint of the rubber sheet member, which has hitherto been made only by hand, and attempts for such automation are proceeding in accodance with this requirement.
For example, it has been proposed in U.S. Pat. No. 4,361,454 that a ply of a rubber sheet member is hung at a front end of a conveyor as a means for feeding the rubber sheet member and then applied onto a former or a joint drum by means of an application roller self-running on an orbit along the outer periphery of the former. However, the moving orbit of the application roller is inseparably related to the outer diameter of the former, so there is a problem in that guide means for the application roller should be provided every a former having a different outer diameter.
Furthermore, disclosed in GB-A-2,108,060 is an application roller for the start-end of the ply and a press roller for the remaining ply or the finish-end thereof are arranged at a front portion and lower portion of a ply feeding table, respectively, together with a mechanism for cutting the ply at a predetermined length. However, the start-end application roller is necessary to produce the deformation for ensuring the contact bonding of the ply start-end to an outer peripheral surface of a tire-building drum (i.e. the use of sponge is necessary), so that there is a problem in durability; otherwise, the bonding of the ply to the drum becomes incomplete and the ply separates from the drum before the ply start-end arrives at the pressure roller. Consequently there is a potential problem concerning the timing of the operation.